What Is a kWh?

A plain-English explanation of a kilowatt-hour (kWh), how it relates to watts, and why it's the unit on your electricity bill.

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Watts and kilowatts

Watts (W) measure how much power something draws at a moment. 1,000 watts is one kilowatt (kW).

A kilowatt-hour (kWh) is the energy used by something drawing 1 kW for one hour. A 2,000 W heater running for 30 minutes also uses 1 kWh.

Suppliers charge you for each kWh you use, which is why it's called the unit rate.

kWh = watts ÷ 1,000 × hours used.